ECO Substation and ESJ 230kV Gen-Tie

The East County Substation (ECO) is a 15-mile transmission corridor project that NV5 has managed since the initial stage of design. ECO consists of 2 new substation sites, approximately 54 steel 138kV poles, and 8 miles of underground 138kV cable. The project is part of a reliability program for a utility agency in the eastern part of San Diego County.

NV5 directed field survey, analysis, and mapping of all properties affected by right-of-way take for the overhead transmission corridor and underground alignment. NV5’s Civil/Structural Engineering group designed the 50% site civil plans for the Boulevard East Substation and 90% plans for all access roads. NV5’s Power group designed all four underground 138kV trench alignments including the two 4.7 mile duct packages coming out of the Boulevard East substation and the 2.7 mile duct packages located on Old Highway 80 near the ECO Substation. NV5 also provided a CYMCAP ampacity study report to detail worst-case ampacity values at each getaway and recommend trench separations to maximize ampacity for each 138kV duct bank. We provided additional survey services including aerial control surveys for the photogrammetric mapping of the substation sites, existing transmission tower locations, staking for the proposed pole locations, and underground trench, access roads, vaults, cable poles, and all Jack & Bore locations.

The ESJ 230kV Gen-Tie Project involved NV5 designing the Gen-Tie overhead tower connection between ECO Substation and the U.S.-Mexico border, where the remainder of the existing Gen-Tie design continued on to a large wind farm in Mexico. The Gen-Tie project was being partly funded by a Southern California utility company, and NV5’s close relationship with the client’s personnel helped facilitate a smooth design process that involved potential hurdles such as language barriers, metric unit conversions, and construction code variations due to the Mexico-based EPC contractor. NV5 provided the following design services for this 3-tower Gen-Tie: survey, grading plan, erosion control plan, drainage study, access roads, tower pads, geotechnical study, tower foundations, tower design, overhead bundled conductor design (via PLS-CADD), OPGW design, grounding design, substation interconnect coordination, SWPPP, construction surveying and support services, and various construction coordination assistance such as processing permits and easements.